Method and apparatus for mapping and/or ablation of cardiac tissue

ABSTRACT

An apparatus for mapping and/or ablating tissue includes a braided conductive member that that may be inverted to provide a ring-shaped surface. When a distal tip of the braided conductive member is retracted within the braided conductive member, the lack of a protrusion allows the ring-shaped surface to contact a tissue wall such as a cardiac wall. In an undeployed configuration, the braided conductive member is longitudinally extended, and in a deployed configuration, the distal end of the braided conductive member is retracted to invert the braided conductive member.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/596,403, entitled “Method and Apparatus for Mapping and/or Ablationof Cardiac Tissue”, filed Jan. 11, 2008, which is a national stage ofPCT Application No. US2005/017337, filed May 17, 2005, which claims thebenefit under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No.60/571,821, entitled “Method And Apparatus For Mapping And/Or AblationOf Cardiac Tissue,” filed on May 17, 2004, each of which is hereinincorporated by reference in its entirety.

BACKGROUND OF INVENTION

1. Field of Invention

The invention relates generally to medical devices for performingmapping and ablation procedures. More particularly, the inventionrelates to methods and apparatus for mapping and/or ablating cardiacwalls.

2. Discussion of Related Art

The human heart is a very complex organ, which relies on both musclecontraction and electrical impulses to function properly. The electricalimpulses travel through the heart walls, first through the atria andthen the ventricles, causing the corresponding muscle tissue in theatria and ventricles to contract. Thus, the atria contract first,followed by the ventricles. This order is essential for properfunctioning of the heart.

Over time, the electrical impulses traveling through the heart can beginto travel in improper directions, thereby causing the heart chambers tocontract at improper times. Such a condition is generally termed acardiac arrhythmia, and can take many different forms. When the chamberscontract at improper times, the amount of blood pumped by the heartdecreases, which can result in premature death of the person.

Techniques have been developed which are used to locate cardiac regionsresponsible for the cardiac arrhythmia, and also to disable theshort-circuit function of these areas. According to these techniques,electrical energy is applied to a portion of the heart tissue to ablatethat tissue and produce scars which interrupt the reentrant conductionpathways or terminate the focal initiation. The regions to be ablatedare usually first determined by endocardial mapping techniques. Mappingtypically involves percutaneously introducing a catheter having one ormore electrodes into the patient, passing the catheter through a bloodvessel (e.g. the femoral vein or artery) and into an endocardial site(e.g., the atrium or ventricle of the heart), and deliberately inducingan arrhythmia so that a continuous, simultaneous recording can be madewith a multichannel recorder at each of several different endocardialpositions.

When an arrythormogenic focus or inappropriate circuit is located, asindicated in the electrocardiogram recording, it is marked by variousimaging or localization means so that cardiac arrhythmias emanating fromthat region can be blocked by ablating tissue. An ablation catheter withone or more electrodes can then transmit electrical energy to the tissueadjacent the electrode to create a lesion in the tissue. One or moresuitably positioned lesions will typically create a region of necrotictissue which serves to disable the propagation of the errant impulsecaused by the arrythromogenic focus. Ablation is carried out by applyingenergy to the catheter electrodes. The ablation energy can be, forexample, RF, DC, ultrasound, microwave, or laser radiation.

Atrial fibrillation together with atrial flutter are the most commonsustained arrhythmias found in clinical practice. Current understandingis that atrial fibrillation is frequently initiated by a focal triggerfrom the orifice of or within one of the pulmonary veins. Though mappingand ablation of these triggers appears to be curative in patients withparoxysmal atrial fibrillation, there are a number of limitations toablating focal triggers via mapping and ablating the earliest site ofactivation with a “point” radiofrequency lesion. One way to circumventthese limitations is to determine precisely the point of earliestactivation. Once the point of earliest activation is identified, alesion can be generated to electrically isolate the trigger with alesion; firing from within those veins would then be eliminated orunable to reach the body of the atrium, and thus could not triggeratrial fibrillation.

Another method to treat focal arrhythmias is to create a continuous,annular lesion around the ostia (i.e., the openings) of either the veinsor the arteries leading to or from the atria, thus “corralling” thesignals emanating from any points distal to the annular lesion.Conventional techniques include applying multiple point sources aroundthe ostia in an effort to create such a continuous lesion. Such atechnique is relatively involved, and requires significant skill andattention from the clinician performing the procedures.

Another source of arrhythmias may be from reentrant circuits in themyocardium itself. Such circuits may not necessarily be associated withvessel ostia, but may be interrupted by means of ablating tissue eitherwithin the circuit or circumscribing the region of the circuit. Itshould be noted that a complete “fence” around a circuit or tissueregion is not always required in order to block the propagation of thearrhythmia; in many cases simply increasing the propagation path lengthfor a signal may be sufficient. Conventional means for establishing suchlesion “fences” include a multiplicity of point-by-point lesions,dragging a single electrode across tissue while delivering energy, orcreating an enormous lesion intended to inactivate a substantive volumeof myocardial tissue.

U.S. Pat. No. 6,315,778 B1, entitled “Apparatus For Creating AContinuous Annular Lesion,” which is herein incorporated by reference,discloses a medical device which is capable of ablating a continuousring of tissue around the ostia of either veins or arteries leading toor from the atria. The medical device includes a protrusion that insertsinto an ostium, thereby allowing electrodes to contact tissue near theostium.

In some instances, it is desirable to perform mapping and/or ablationprocedures on a cardiac wall (or other tissue) that is not located nearan ostium. In such a scenario, the lack of a protrusion may help toallow electrodes of a device contact the cardiac wall or other tissue.In other cases, mapping and/or ablation may be desired at severallocations around an ostium and it would be helpful to be able toposition electrodes without concern for a protrusion that may hindercontact between electrodes and the cardiac wall.

SUMMARY OF INVENTION

Embodiments of the present invention encompass apparatus and methods formapping electrical activity within the heart. Embodiments of the presentinvention also encompass methods and apparatus for creating lesions inthe heart tissue (ablating) to create a region of necrotic tissue whichserves to disable the propagation of errant electrical impulses causedby an arrhythmia. The apparatus and methods described herein also may beused for mapping and ablating of tissue other than heart tissue.

One embodiment of the invention is directed to a medical device forelectrophysiology procedures, comprising a catheter shaft having aproximal end and a distal end. The braided conductive member is locatedat the catheter shaft distal end and the braided conductive member hasan undeployed configuration in which the braided conductive member has adistal end and is in a longitudinally extended configuration. Thebraided conductive member further includes a deployed configuration inwhich the braided conductive member distal end is positioned proximallyrelative to portions of the to braided conductive member.

According to some embodiments, the braided conductive member compriseselectrically conductive filaments. The braided conductive member maycomprise mapping filaments and/or ablation filaments. In the deployedconfiguration, the braided conductive member may form a distally-facingsurface with nothing protruding distally beyond the distally-facingsurface.

According to some embodiments, the medical device further comprises abraided conductive member adjustment element constructed and arranged tomove the braided conductive member distal end. The braided conductivemember adjustment element may be a cable attached to the braidedconductive member distal end, the cable being constructed and arrangedto pull the braided conductive member distal end in a proximaldirection. In the deployed configuration, the braided conductive membermay form a distally-facing ring-shaped surface that is substantiallyperpendicular to a longitudinal direction of the braided conductivemember. The medical device may further comprise a sheath that isadvanceable over and retractable from the braided conductive member. thedistal end of the catheter shaft may be steerable in some embodiments.

According to some embodiments, the medical device further comprisessupport elements within a proximal portion of the braided conductivemember. The braided conductive member may be radiallyasymmetrically-shaped relative to a longitudinal axis of the braidedconductive member. The braided conductive member may be longitudinallyasymmetrically-shaped relative to a longitudinal axis of the braidedconductive member. The medical device may further comprise a controlleroperatively connected to the braided conductive member. The medicaldevice may further comprise an irrigation system.

According to a further embodiment of the invention, a catheter comprisesa catheter shaft having a proximal end and a distal end, and a braidedconductive member located at the catheter shaft distal end. The braidedconductive member has an undeployed configuration in which a distal endof the braided conductive member is everted. The braided conductivemember also has a deployed configuration in which a portion the braidedconductive member is inverted.

In some embodiments, in the deployed configuration, the braidedconductive to member forms a distal ring of filaments. In someembodiments, in the deployed configuration, nothing protrudes distallyfrom the distal ring. In the deployed configuration, the distal ring maybe arranged such that it contactable to a substantially flat area oftissue that has no ostia.

According to another embodiment of the invention, an apparatus comprisesa catheter shaft having a distal end, and a braided conductive memberdisposed at the distal end of the catheter shaft. The braided conductivemember comprises a plurality of filaments extending from a proximalanchoring location to a distal attachment location. The braidedconductive member has a maximum diameter that is a first distance fromthe distal attachment location, the maximum diameter being a second,larger distance from the proximal anchoring location when the braidedconductive member is in a relaxed state, and the distal attachmentportion is retractable to radially expand the braided conductive memberand to invert the braided conductive member.

According to yet another embodiment of the invention, an apparatuscomprises a catheter shaft having a distal end, and a braided conductivemember disposed at the distal end of the catheter shaft. The braidedconductive member comprises a plurality of filaments extending from aproximal anchoring location to a distal attachment location, the braidedconductive member having a maximum diameter that is longitudinallylocated more than two-thirds of the distance from the proximal anchoringlocation to the distal attachment location when the braided conductivemember is in a relaxed state.

According to another embodiment of the invention, a method ofpositioning a braided conductive member within a patient comprises stepsof introducing a braided conductive member into a patient in a firstconfiguration in which a distal end of the braided conductive member iseverted, and inverting the braided conductive member to place thebraided conductive member in a second, deployed configuration in whichthe braided conductive member forms a distal annular surface withnothing protruding distally beyond the distal annular surface.

The method may further comprise retracting a sheath to expose thebraided conductive member. In some embodiments, the step of invertingthe braided conductive member distal end comprises actuating a braidedconductive member adjustment element. Actuating the braided conductivemember adjustment element may comprise pulling a cable attached to adistal end of the braided conductive member. In some embodiments, themethod further comprises contacting the distal annular surface of thebraided conductive member to cardiac tissue. The method may includedetecting electrical impulses with the braided conductive member andtransmitting the electrical impulses to a recording device. A step ofactivating a plurality of filaments that are part of the braidedconductive member to ablate cardiac tissue may also be included as partof the method.

According to a further embodiment of the invention, a method ofcontacting cardiac tissue with a ring-shaped surface of a braidedconductive member comprises steps of: introducing into a patient acatheter having a proximal end, a distal end, and a braided conductivemember; configuring the braided conductive member such that it has adistally-facing, ring-shaped surface of filaments with nothingprotruding distally from the distally-facing, ring-shaped surface; andcontacting the distally-facing, ring-shaped surface to cardiac tissue.

The method may further comprise activating filaments of the braidedconductive member to ablate the cardiac tissue and/or mapping electricalimpulses with filaments of the braided conductive member.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, like components that are illustrated in various figures arerepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing. In the drawings:

FIG. 1 illustrates an overview of a mapping and ablation catheter systemin accordance with one embodiment of the present invention;

FIG. 2 illustrates a braided conductive member in an undeployed stateaccording to one embodiment of the invention;

FIG. 3 illustrates a braided conductive member in a partially expandedstate according to one embodiment of the invention;

FIG. 4 illustrates a braided conductive member in an inverted stateaccording to one embodiment of the invention;

FIG. 5 illustrates a braided conductive member in an inverted statewhere a distal end of the braided conductive member does not protrudedistally from the inverted braided conductive member according to oneembodiment of the invention;

FIG. 6 illustrates a braided conductive member including supportelements according to one embodiment of the invention;

FIG. 7 illustrates a braided conductive member according to anotherembodiment of the invention;

FIG. 8 illustrates an alternate embodiment of the braided conductivemember according to another embodiment of the invention;

FIG. 9 illustrates the use of irrigation according to one embodiment ofthe invention;

FIG. 10 illustrates the use of irrigation according to anotherembodiment of the invention;

FIG. 10A is an enlarged cross-sectional view of a filament used in thebraided conductive member illustrated in FIG. 10; and

FIG. 11 illustrates one embodiment of a method of using a catheter andthe braided conductive member.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components and acts set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” or “having,”“containing”, “involving”, and variations thereof herein, is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items.

System Overview

Reference is now made to FIG. 1, which illustrates an overview of amapping and/or ablation catheter system in accordance with oneembodiment of the present invention. The system includes a catheter 10having a shaft portion 12, a control handle 14, a connector portion 16,and a braided conductive member 28. A controller 8 is connected toconnector portion 16 via cable 6. Ablation energy generator 4 may beconnected to controller 8 via cable 3. A recording device 2 may beconnected to controller 8 via cable 1. When used in an ablationapplication, controller 8 is used to control ablation energy provided tocatheter 10 by ablation energy generator 4. When used in a mappingapplication, controller 8 is used to process signals coming fromcatheter 10 and to provide these signals to recording device 2. Althoughillustrated as separate devices, recording device 2, ablation energygenerator 4, and controller 8 could be incorporated into a single deviceor two devices.

In this description, various aspects and features of the presentinvention will be described. The various features of the invention arediscussed separately for clarity. One skilled in the art will appreciatethat the features may be selectively combined in a device depending uponthe particular application. Furthermore, any of the various features maybe incorporated in a catheter and associated method of use for eithermapping and/or ablation procedures.

Catheter Overview

Reference is now made to FIGS. 2-5, which illustrate one embodiment ofthe present invention. Embodiments of the present invention generallyinclude a catheter and methods of its use for mapping and ablation inelectrophysiology procedures. FIG. 2 illustrates braided conductivemember 28 in an unexpanded state. In this embodiment, the unexpandedstate of the braided conductive member is an undeployed configuration.Braided conductive member 28 is, in one embodiment of the invention, aplurality of interlaced, electrically conductive filaments 34 which areattached at a distal end 18 with a cap 24 and also at a proximal end 19with an anchoring element 32. Of course any suitable element or methodmay be used to attach or anchor filaments 34. FIG. 3 illustrates braidedconductive member 28 in a partially expanded state. Each of FIGS. 2 and3 show a state in which braided conductive member 28 is completelyeverted. FIG. 4 illustrates braided conductive member 28 in a firstdeployed configuration option which may be used to locate braidedconductive member 28 at an ostium. In FIG. 4, distal end 18 of braidedconductive member 28 is partially inverted. The terms “partially invert”and “partially inverted”, for purposes herein, refer to a configurationin which portions of filaments are retracted within the braidedconductive member such that they are at least partially surrounded byother portions of filaments. A tip, or other portions of the braidedconductive member may protrude distally from any distally-facing surfaceof the braided conductive member when the braided conductive member ispartially inverted. FIG. 5 illustrates braided conductive member 28 in asecond deployed configuration option which may be used to effect contactbetween an annular surface of braided conductive member 28 and a cardiacwall (see, for example, FIG. 11) other cardiac tissue, or other targettissue. In FIG. 5, the distal tip of braided conductive member 28 isinverted. The terms “invert” or “inverted”, for purposes herein, referto a configuration in which the distal tip or distal end of the braidedconductive member is retracted such that the distal tip does notprotrude distally from a distally-facing surface of the braidedconductive member. For purposes herein, the terms “evert” or “everted”refer to a configuration in which the distal tip or distal end of thebraided conductive member protrudes distally from any distally-facingannular surface that is present. An everted configuration does not,however, require that a distally-facing annular surface be present. Insome embodiments, such as the embodiment illustrated in FIG. 2, thebraided conductive member is fully elongated in an evertedconfiguration. The term “completely everted”, when referring to a distalregion of a braided conductive member, refers to a configuration inwhich no portion of the distal region of the braided conductive memberis inverted within itself.

A braided conductive member adjustment element, such as a cable 22, isattached to distal end 18 of braided conductive member 28. Cable 22 mayextend through a lumen (not shown) in shaft portion 12 and through theinterior of braided conductive member 28. Cable 22 may be attached todistal end 18 of braided conductive member 28 using cap 24, an anchorband, or any suitable attachment or anchoring element or method known inthe art. At the control handle end, cable 22 may be attached to acontrol element, such as a slide actuator for example, that allows auser to retract and advance cable 22. It should be noted that cable 22is a separate element from cables 1, 3 and 6. Of course, braidedconductive member adjustment element need not be a cable as any suitableelement for adjusting the braided conductive member may be used. Forexample, a sheath may be used to push the braided conductive member overthe distal tip of the braided conductive member to invert braidedconductive member 28.

In operation, moving cable 22 in the proximal direction causes braidedconductive member 28 to compress longitudinally and/or to expandradially, as shown in FIG. 3. Further proximal movement of cable 22causes a portion of braided conductive to member 28 to invert as shownin FIG. 4. Even further proximal movement of cable 22 may retract distalend 18 such that distal end 18 is encircled by a portion of braidedconductive member 28. In some embodiments, distal end 18 may besurrounded or partially surrounded by a portion of braided conductivemember 28 that does not form a circle.

In some embodiments, a certain amount of movement of cable 22 in theproximal direction may occur without user actuation due to the bias ofthe braided conductive member 28. For example, braided conductive member28 may be longitudinally extended beyond a relaxed state by radiallycompressing braided conductive member 28 with a sheath 33 (see FIG. 2).Upon retraction of sheath 33, braided conductive member 28 may radiallyexpand a certain amount due to its filament winding structure, or due toelastic or spring elements attached to the filaments. In furtherembodiments, cable 22 may be used to urge braided conductive member 28back into a longitudinally extended state by pushing on cap 24 or otherdistal attachment portion.

By retracting distal end 18 of braided conductive member 28 at least acertain distance in the proximal direction, a braided conductive memberannular surface 30 may be formed in a plane that is substantiallyperpendicular to a distal end 26 of shaft portion 12, as illustrated inFIG. 4. Retracting distal end 18 further removes the projection ofdistal end 18 beyond annular surface 30, as illustrated in FIG. 5, whichmay allow annular surface 30 to be placed in contact with a cardiac wallor other cardiac tissue. If braided conductive member 28 is onlypartially inverted and distal end 18 projects beyond annular surface 30in the distal direction, it may hinder efforts to contact cardiac tissuewith the annular surface. In some embodiments, however, it may bedesirable to maintain a portion of distal end 18 projecting from braidedconductive member 28 so that braided conductive member 28 may bepositioned relative to an ostium by inserting distal end 18 into theostium. In some embodiments, the annular surface may be arranged suchthat it is contactable to a substantially flat area of tissue that hasno ostia, even though an element may protrude distally from the annularsurface. For example, a highly flexible element, such as a touch sensor,may protrude distally from the inverted braided conductive member andthe annular surface would still be arranged such that it is contactableto a substantially flat area of tissue that has no ostia. The touchsensor may be a bend sensor that is positioned on the distal tip of thebraided conductive member and protrudes slightly from thedistally-facing surface when the braided conductive member is put into adeployed configuration. The bend sensor bends upon encountering a tissuewall and signals the controller that it has bent. The flexibility of thebend sensor allows the braided conductive member to contact the wall.

For purposes herein, a “surface” of braided conductive member 28 refersto a plurality of interlaced conductive elements, such as filaments orwires, even though the interlaced elements may not fully occupy thespace considered to be the surface. In some embodiments, wires or otherconductive elements may be attached to or embedded in a flexible supportmaterial such that a solid surface is present.

The annular surface formed by inverting the braided conductive member 28may have electrodes spaced around the entire annular surface. In otherembodiments, electrodes may be positioned only on a portion or portionsof the ring-shaped surface.

As illustrated in FIGS. 2-5, a sheath 33 may be provided. Sheath 33serves to protect shaft portion 12 and braided conductive member 28during manipulation through the patient's vasculature. In addition,sheath 33 may shield braided conductive member 28 from the patient'stissue in the event ablation energy is prematurely delivered to thebraided conductive member 28.

Sheath 33 may be advanced and retracted over shaft portion 12 in anysuitable manner. Control handle 14 may be used to effect the advancementor retraction of sheath 33. U.S. Pat. Nos. 5,383,852, 5,462,527, and5,611,777, which are herein incorporated by reference in theirentireties, illustrate examples of control handles that can controlsheath 33. As described in these patents, control handle 14 may includea slide actuator which is axially displaceable relative to the handle.The slide actuator may be connected to sheath 33 to retract sheath 33 toexpose braided conductive member 28 once the distal end of the catheterhas been positioned within the heart or other target location.

Braided conductive member 28 may be shaped or biased such that whensheath 33 is retracted, braided conductive member 28 expands slightly inthe radial direction. In other embodiments, braided conductive member 28may maintain its longitudinally extended shape until cable 22 or otheradjustment element is pulled in the proximal direction to longitudinallycompress braided conductive member 28. In still other embodiments,braided conductive member 28 may maintain a radial size similar to itsrelaxed state radial size when distal tip 18 is moved proximally, oreven when braided conductive member 28 is inverted.

Braided conductive member 28 is, in one embodiment of the invention, aplurality of interlaced, electrically conductive filaments 34. In someembodiments, braided conductive member 28 is a wire mesh. The filaments34 are preferably formed of metallic elements having relatively smallcross sectional diameters, such that the filaments are flexible and thebraided conductive member can be expanded radially outwardly. In oneembodiment, the filaments may be round in cross-section, having adimension on the order of about 0.001-0.030 inches in diameter.Alternatively, the filaments may have flat sides in cross-section, withthicknesses on the order of about 0.001-0.030 inches, and widths on theorder of about 0.001-0.030 inches. The filaments may be formed ofnitinol-type wire or other shaped memory alloys. Alternatively, thefilaments may include non-metallic elements woven with metallicelements, with the non-metallic elements providing support to and/orseparation of the metallic elements. A multiplicity of individualfilaments 34 may be provided in braided conductive member 28, forexample three hundred or more filaments. Instead of a multiplicity orplurality of filaments, a smaller number of filaments, or even only onecontinuous filament may be arranged to form braided conductive member28. For purposes herein, the terms “filaments” or “plurality offilaments” may refer to one continuous filament that is interlaced withitself to form a braided conductive member.

Each of the filaments 34 may be electrically isolated from each other byan insulation coating. This insulation coating may be, for example, apolyamide type material. In one manner of forming an electrode, aportion of the insulation on the filaments forming an outercircumferential surface of braided conductive member 28 is removed. Thisarrangement allows each of the filaments 34 to form an isolatedelectrode, not in electrical contact with any other filament, that maybe used for mapping and ablation. In some embodiments, an electrode maycontact a coated section of another filament. Alternatively, specificelectrodes may be permitted to contact each other to form a preselectedgrouping. Methods of removing insulation from filaments 34 are disclosedin PCT Publication No. WO 02/087437, which is herein incorporated byreference in its entirety. The insulation may also be removed in apreferential manner so that a particular portion of the circumferentialsurface of a filament 34 is exposed. In this manner, when braidedconductive member 28 is radially expanded, the stripped portions to offilaments may preferentially face an intended direction of mapping orablation.

Further, in some embodiments to the invention, some of filaments 34 maybe used for mapping or electrical measurement, while others of filaments34 may be used for ablation. The mapping and ablation filaments may beactivated independently or may be activated concurrently. Oneapplication of dedicating some filaments for mapping and others forablation is using a single braided conductive member 28 to both form alesion and measure the quality of the lesion. Such an arrangement canavoid a change of catheters during a medical procedure. Temperaturesensors (not shown) also may be included on catheter shaft 12 or braidedconductive member 28.

A wire (not shown) may run from each of the filaments 34 to connectorportion 16 via conductors (not shown). A multiplexer or switch box maybe connected to the conductors so that each filament 34 may becontrolled individually. This function may be incorporated intocontroller 8. In some embodiments, a number of filaments 34 may begrouped together for mapping and ablation. Alternatively, eachindividual filament 34 may be used as a separate mapping channel formapping individual electrical activity at a single point. Using a switchbox or multiplexer to configure the signals being received by filaments34 or ablation energy sent to filaments 34 results in a large number ofpossible combinations of filaments for detecting electrical activityduring mapping procedures and for applying energy during an ablationprocedure.

Catheter 10 may also have a reference electrode (not shown) mounted onshaft 12 so that reference the reference electrode is located outsidethe heart during unipolar mapping operations.

Individual control of the electrical signals received from filaments 34allows catheter 10 to be used for bipolar (differential or betweenfilament) type mapping as well as unipolar (one filament with respect toa reference electrode) type mapping.

Catheter 10 may be a steerable device, in some embodiments, in that thedistal end 26 may be deflected by an actuator contained within controlhandle 14. Control handle 14 may include a rotatable thumb wheel whichcan be used by a user to deflect distal end 26 of the catheter. Thethumb wheel (or any other suitable actuating device) is connected to oneor more pull wires (not shown) which extend through shaft portion 12 andconnect to distal end 18 of the catheter at an off-axis location,whereby tension applied to one or more of the pull wires causes thedistal portion of the catheter to curve in a predetermined direction ordirections. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777illustrate various embodiments of control handle 14 that may be used forsteering catheter 10.

In some embodiments, a proximal portion of braided conductive member 28includes support elements to aid in maintaining the shape and/orstructural integrity of portions of braided conductive member 28 whendistal end 18 is moved in the proximal direction. For example, supportelements may include support filaments 34′ that are stronger, thicker ormore rigid at their proximal ends than at their distal ends, asillustrated in FIG. 6. In other embodiments, splines 35 or othernon-filament elements may be included, such as by interlacing supportelements among filaments 34, as illustrated in FIG. 7. In still furtherembodiments, support elements which are not interlaced with filaments 34may be included. In some embodiments, support elements attach to aproximal anchoring element 32 at a first end and to cap 24 or filaments34 at a second end.

Referring to FIG. 7, an embodiment of the invention having alongitudinally asymmetrically shaped braided conductive member 28 isillustrated. In this embodiment, a maximum diameter 36 of braidedconductive member 28 is located closer to distal end 18 than to proximalanchoring element 32. In one embodiment, maximum diameter 36 islongitudinally located more than two-thirds of the way from the proximalanchoring location to the distal attachment location. As cable 22 isdrawn in the proximal direction to move cap 24, splines 35 support themore proximal region of braided conductive member 28.

Reference is now made to FIG. 8 which illustrates another shape ofbraided conductive member 28. As described above regarding variousembodiments of the invention, braided conductive member 28 may begenerally radially symmetrical. However, certain anatomical structuresmay have complex three-dimensional shapes that are not easilyapproximated by a geometrically symmetrical mapping or ablationstructure. To successfully contact these types of anatomical structures,braided conductive member 28 can be “preformed” to a close approximationof that anatomy, and yet still be flexible enough to adapt to variationsfound in specific patients. Alternatively, braided conductive member 28can be of sufficient strength (as by choice to of materials,configuration, etc.) to force the tissue to conform to variations foundin specific patients. For example, FIG. 8 illustrates braided conductivemember 28 disposed about shaft 12 in an off-center or non-concentricmanner such that braided conductive member 28 is radiallyasymmetrically-shaped. In addition, braided conductive member 28 mayalso be constructed so that the annular surface of the braidedconductive member in its expanded configuration is a non-circularsurface so as to improve tissue contact. FIG. 8 illustrates an exampleof this type of configuration where the braided conductive member 28 isconstructed and arranged to be non-concentric with respect to alongitudinal axis of braided conductive member 28 and also, in itsexpanded configuration, to have an asymmetric shape. In someembodiments, the asymmetric expanded configurations and the eccentricityof braided conductive member 28 with respect to the longitudinal axiscan be produced by providing additional structural supports in braidedconductive member 28, for example, by adding nitinol wire, ribbon wire,splines, and so on. Other suitable methods of creating the eccentricand/or asymmetric shape include: varying the winding pitch; varyingindividual filament size and/or placement; deforming selective filamentsin braided conductive member 28; and any other suitable method known tothose skilled in the art.

An asymmetrically-shaped braided conductive member may allow for theformation of a ring-shaped surface that is disposed at an angle togeneral longitudinal direction of the braided member and/or the distalend of the catheter. The angled surface may permit better contact withcertain tissue areas. In still other embodiments, inverting the braidedconductive member may form a non-planar surface. For example, differingfilament diameters may allow for the formation of a ring-shaped surfacewhich includes a section that is substantially perpendicular to thecatheter and a section that is disposed at an angle to the catheter. Theangle of the surface relative to the catheter may change continuouslyacross the surface in still other embodiments.

In some embodiments of the present invention, catheter 10 may be coatedwith a number of coatings that enhance the operating properties ofbraided conductive member 28. The coatings may be applied by any of anumber of techniques and the coatings may include a wide range ofpolymers and other materials.

Braided conductive member 28 may be coated to reduce its coefficient offriction, thus reducing the possibility of thrombi adhesion to thebraided conductive member as well as the possibility of vascular oratrial damage. These coatings can be combined with insulation (ifpresent) on the filaments that make up braided conductive member 28.These coatings may be included in the insulation itself, or the coatingsmay be applied over the insulation layer.

Braided conductive member 28 also may be coated to increase or decreaseits thermal conduction, which can improve the safety or efficacy of thebraided conductive member 28. This change in thermal conduction may beachieved by incorporating thermally conductive elements or thermallyinsulating elements into the electrical insulation of the filaments thatmake up braided conductive member 28, or by adding a coating to theassembly. Polymer mixing, IBAD, or similar technology could be used toadd Ag, Pt, Pd, Au, Ir, Cobalt, and others into the insulation or tocoat braided conductive member 28.

In some embodiments, radioopaque coatings or markers may be used toprovide a reference point for orientation of braided conductive member28 when viewed during fluoroscopic imaging. The materials that provideradiopacity including, for example, Au, Pt, Ir, and others known tothose skilled in the art. These materials may be incorporated and usedas coatings as described above.

Antithrombogenic coatings, such as heparin and BH, can also be appliedto braided conductive member 28 to reduce thrombogenicity to preventblood aggregation on braided conductive member 28. These coatings can beapplied by dipping or spraying, for example.

As noted above, the filament 34 of braided conductive member 28 may beconstructed of metal wire materials. These materials may be, forexample, MP35N, nitinol, or stainless steel. Filaments 34 may also becomposites of these materials in combination with a core of anothermaterial such as silver or platinum. The combination of a highlyconductive electrical core material with another material forming theshell of the wire allows the mechanical properties of the shell materialto be combined with the electrical conductivity of the core material toachieve better and/or selectable performance. The choice and percentageof core material used in combination with the choice and percentage ofshell material used can be selected based on the desired performancecharacteristics and mechanical/electrical properties desired for aparticular application.

There may be times during ablation or mapping procedures when catheter10 passes through difficult or tortuous vasculature. During these times,it may be helpful to have a guiding sheath (not shown) through which topass catheter 10 so as to allow easier passage through the patient'svasculature.

Irrigation

It is known that for a given electrode side and tissue contact area, thesize of a lesion created by radiofrequency (RF) energy is a function ofthe RF power level and the exposure time. At higher powers, however, theexposure time can be limited by an increase in impedance that occurswhen the temperature at the electrode-tissue interface approaches a 100°C. One way of maintaining the temperature less than or equal to thislimit is to irrigate the ablation electrode with saline to provideconvective cooling so as to control the electrode-tissue interfacetemperature and thereby prevent an increase in impedance. Accordingly,irrigation of braided conductive member 28 and the tissue site at whicha lesion is to be created can be provided in the present invention. FIG.9 illustrates the use of an irrigation manifold within braidedconductive member 28. An irrigation manifold 100 is disposed along shaft12 inside braided conductive member 28. Irrigation manifold 100 may beone or more polyimide tubes. Within braided conductive member 28, theirrigation manifold splits into a number of smaller tubes 102 that arewoven into braided conductive member 28 along a respective filament 34.A series of holes 104 may be provided in each of the tubes 102. Theseholes can be oriented in any number of ways to target a specific site orportion of braided conductive member 28 for irrigation. Irrigationmanifold 100 runs through catheter shaft 12 and may be connected to anirrigation delivery device outside the patient used to inject anirrigation fluid, such as saline, for example, such as during anablation procedure.

The irrigation system can also be used to deliver a contrast fluid forverifying location or changes in vessel diameter. For example, acontrast medium may be perfused prior to ablation and then after anablation procedure to verify that there have been no changes in theblood vessel diameter. The contrast medium can also be used duringmapping procedures to verify placement of braided conductive member 28.In either ablation or mapping procedures, antithrombogenic fluids, suchas heparin can also be perfused to reduce thrombogenicity.

FIG. 10 illustrates another way of providing perfusion/irrigation incatheter 10. As illustrated in FIG. 10, the filaments 34 that comprisebraided conductive member 28 may be composed of a composite wire 110.The composite wire 110 includes a lumen 114 containing an electricallyconductive wire 112 that is used for delivering ablation energy in anablation procedure or for detecting electrical activity during a mappingprocedure. Composite wire 110 also contains a perfusion lumen 116.Perfusion lumen 116 is used to deliver irrigation fluid or a contrastfluid as described in connection with FIG. 9. Once braided conductivemember 28 has been constructed with composite wire 110, the insulation118 surrounding wire filament 112 can be stripped away to form anelectrode surface. Holes can then be provided into perfusion lumen 116to then allow perfusion at targeted sites along the electrode surface.As with the embodiment illustrated in FIG. 9, the perfusion lumens canbe connected together to form a manifold which manifold can then beconnected to, for example, perfusion tube 120 and connected to a fluiddelivery device.

Methods of Use

Reference is now made to FIG. 11 which illustrates how a catheteraccording to certain embodiments of the present invention may be used inendocardial applications.

In an endocardial procedure, shaft portion 12 is introduced into apatient's heart 150. Appropriate imaging guidance (direct visualassessment, camera port, fluoroscopy, echocardiographic, magneticresonance, etc.) can be used. FIG. 11 in particular illustrates shaftportion 12 being placed in the left atrium of the patient's heart. Onceshaft portion 12 reaches the patient's left atrium, sheath 33 may beretracted and braided conductive member 28 may be inverted to itsdeployed state, where, in the illustrated embodiment, braided conductivemember 28 forms a cone-type shape including a distally-facing,ring-shaped surface. External pressure may be applied along shaftportion 12 to achieve the desired level of contact between braidedconductive member 28 and the cardiac tissue. In one embodiment, mappingof electrical impulses may be achieved with braided conductive member28. In another embodiment, energy is applied to the cardiac tissue incontact with braided conductive member 28 to create an annular lesion.The energy used may be RF (radiofrequency), DC, microwave, ultrasonic,cryothermal, optical, etc.

In some embodiments, the braided conductive member may be configuredsuch that it forms a distally-facing, ring-shaped surface before thebraided conductive member is introduced to the heart.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art. Such alterations, modifications, and improvements are intendedto be part of this disclosure, and are intended to be within the spiritand scope of the invention. Accordingly, the foregoing description anddrawings are by way of example only.

1. A medical device for electrophysiology procedures, comprising: acatheter shaft having a proximal end and a distal end; and a braidedconductive member located at the catheter shaft distal end; the braidedconductive member having an undeployed configuration in which thebraided conductive member has a distal end and is in a longitudinallyextended configuration; the braided conductive member further having adeployed configuration in which the braided conductive member distal endis positioned proximally relative to portions of the braided conductivemember; and a braided conductive member adjustment element configured topull the distal end of the braided conductive member in a proximaldirection to place the braided conductive member in to the deployedconfiguration; wherein in the deployed configuration, the braidedconductive member forms a distally-facing ring-shaped surface andincludes ablation electrodes configured to form an annular lesion intissue when the distally-facing surface is contacted to the tissue andthe ablation electrodes are activated.
 2. A medical device according toclaim 1, wherein the braided conductive member comprises electricallyconductive filaments.
 3. A medical device according to claim 1, whereinthe braided conductive member comprises mapping filaments.
 4. A medicaldevice according to claim 1, wherein the ablation electrodes compriseablation filaments.
 5. A medical device according to claim 4, whereinthe braided conductive member further comprises mapping filaments.
 6. Amedical device as in claim 1, wherein, in the deployed configuration,nothing protrudes distally beyond the distally-facing surface.
 7. Amedical device as in claim 1, wherein, in the deployed configuration,the braided conductive member forms a distal ring of filaments.
 8. Amedical device as in claim 1, wherein the braided conductive memberadjustment element is a cable attached to the braided conductive memberdistal end, the cable being constructed and arranged to pull the braidedconductive member distal end in a proximal direction.
 9. A medicaldevice as in claim 1, wherein, in the deployed configuration, thedistally-facing ring-shaped surface is substantially perpendicular to alongitudinal direction of the braided conductive member.
 10. A medicaldevice as in claim 1, further comprising a sheath that is advanceableover and retractable from the braided conductive member.
 11. A medicaldevice as in claim 1, wherein the distal end of the catheter shaft issteerable.
 12. A medical device as in claim 1, further comprisingsupport elements within a proximal portion of the braided conductivemember.
 13. A medical device as in claim 1, wherein the braidedconductive member is radially asymmetrically-shaped relative to alongitudinal axis of the braided conductive member.
 14. A medical deviceas in claim 1, wherein the braided conductive member is longitudinallyasymmetrically-shaped relative to a longitudinal axis of the braidedconductive member.
 15. A medical device as in claim 1, furthercomprising a controller operatively connected to the braided conductivemember.
 16. A medical device as in claim 1, further comprising anirrigation system.
 17. A catheter comprising: a catheter shaft having aproximal end and a distal end; and a braided conductive member locatedat the catheter shaft distal end; the braided conductive member havingan undeployed configuration in which a distal end of the braidedconductive member is everted; the braided conductive member furtherhaving a deployed configuration in which a portion the distal end of thebraided conductive member is inverted; wherein in the deployedconfiguration, the braided conductive member forms a distally-facingring-shaped surface and includes ablation electrodes configured to forman annular lesion in tissue when the distally-facing surface iscontacted to the tissue and the ablation electrodes are activated; andin the deployed configuration with nothing protruding distally beyondthe distal annular surface.
 18. A catheter as in claim 17, wherein, inthe deployed configuration, the braided conductive member forms a distalring of filaments.
 19. A catheter as in claim 18, wherein, in thedeployed configuration, the distal ring is arranged such that itcontactable to a substantially flat area of tissue that has no ostia.20. A medical device for electrophysiology procedures, comprising: acatheter shaft having a proximal end and a distal end; a braidedconductive member located at the catheter shaft distal end; a sheaththat is advanceable over and retractable from the braided conductivemember; and a controller operatively connected to the braided conductivemember; the braided conductive member having an undeployed configurationin which the braided conductive member has a distal end and is in alongitudinally extended configuration; the braided conductive memberfurther having a deployed configuration in which the braided conductivemember distal end is positioned proximally relative to portions of thebraided conductive member; wherein in the deployed configuration, thebraided conductive member forms a distally-facing ring-shaped surfaceand includes ablation electrodes configured to form an annular lesion intissue when the distally-facing surface is contacted to the tissue andthe ablation electrodes are activated.